Deformation compensating hydraulic device for rolling mills of the hydraulic mechanical pressure type



Nov. 22, 1966 DIOLOT DEFORMATION COMPENSATING HYDRAULIC DEVICE FOR ROLLING MILLS OF THE HYDRAULIC MECHANICAL PRESSURE TYPE Filed Feb. 7, 1964 I/llllllllt I! I,

United States Patent 8 Claims. or. 72- s This invention relates to rolling mills having hydromechanical screwdown systems and more particularly concerns an electro-mechanically actuated hydraulic system to compensate for the roll deformation during the rolling operation.

In rolling mills having a hydro-mechanical screwdown system of current type, the distance between the chocks is initially set at each end of the roll stand by means of ram cylinders of the short stroke, large section type, each being connected through hydraulic conduits to a screwdown cylinder of the long stroke, small section type. The pistons of the screwdown cylinders are driven by electric motors, the output of which, as it is well-known by those skilled in the art, may be substantially less than that of the motors used in non-hydraulic screwdown systems of equivalent efficiency.

The use of low output electric motors in hydraulic screwdown systems lead to the development of the continuous compensation for changes in the roll clearance due to roll deformations during passes. It was found that the response of the small output screwdown motors triggered by electric signals generated in turn by the variations in the roll deformation was very rapid, but an instantaneous pressure compensation was hinder-ed by the limited rotational speed of these motors.

It is therefore a primary object of the invention to 7 provide an improved hydraulic system for use in rolling mills to continuously and instantaneously compensate for roll deformations during passes.

It is a further object of the invention to provide in rolling mills an improved hydraulic compensation system operable independently and with the exclusion of the screwdown mechanism.

Briefly, the invention provides a hydraulic conduit communicating with the ram cylinder in each chock and an equalizing cylinder, electric means for sensing the pressure fluctuations in the ram cylinders due to roll deformations, and means for electrically actuating a valve mechanism in response to the electrically sensed pressure fluctuations, said valve being adapted to control the admission of servo pressure into a control cylinder to counteract the fluctuating pressures caused .by the roll deformation.

The invention will be better understood when reference is had to the ensuing specification taken in conjunction with the drawing wherein the single figure is a schematic representation of a preferred embodiment according to the invention.

Referring now to the drawing, there is shown a pair of upstanding spaced roll stands 1 and 1 of a two-high rolling mill. Each stand 1, 1' supports a lower chock 2, 2' and an upper chock 3, 3, respectively. Between each of the lower chocks 2, 2' there is positioned a lower working roll 4, While between the upper chocks 3, 3' there extends an upper working roll 4'. With each lower chocks 2, 2' there is associated a conventional short stroke, large section type hydraulic ram cylinder 6, 6'. The screwdown pressure in the two rarn cylinders 6, 6' is set by the screwdown cylinders 7, 7', the pistons of which, in turn, are advanced or retracted by electric screwdown motors 9, 9' linked to the pistons by means of a reduction gear assembly 8, 8', respectively. The motors 9, 9' are interconnected by a clutch 10, generally of the magnetic type. Screwdown cylinder 7 and ram cylinder 6 are connected through a hydraulic conduit 11, While screwdown cylinder 7' communicates with ram cylinder 6' by means of a hydraulic conduit 11.

The precedingly described details are typical of rolling mills that incorporate a hydraulic screwdown system presently in their use.

Ram cylinders 6 and 6 further communicate through conduits 12, 12' with the right hand chamber of equalizing cylinders l3, 13', respectively. In both equalizing cylinders 13, 13' there is slid-ably disposed a piston the function of which will become apparent as the specification progresses. The piston in both equalizing cylinders 13, 13' are, on one hand, mechanically interconnected and are, on the other hand, joined with the piston of a control cylinder 14. The mechanical linkage between the pistons in cylinders 13, 13 and 14 may be etfectuated simply by arranging said cylinders along the same axis and joining the three pistons with a single rod 2% It is well understood that the spaced relation and the axial disposition of cylinders 13, 13' and 14 described hereinbefore and schematically illustrated in the drawing should by no means be construed as limiting the inventive system. For example, the three cylinders 13, 13' and 14 may be replaced by an equivalent unitary device having expansible chambers and mechanically interconnected pistons slidable therein.

Referring once again to the drawing, the control cylinder 14 is associated with a second hydraulic circuit independent of, and separated from the precedingly described screwdown circuit. This second hydraulic circuit comprises a reservoir 18, a pressure accumulator 16 supplied with hydraulic liquid from reservoir 18 by means of a pump 17. The second hydraulic circuit further comprises a solenoid valve 15 which controls the admission of hydraulic liquid into cylinder 14 in a manner as will be explained hereinafter.

At least one of the ram cylinders 6, 6' is connected to a pressure gauge 22 adapted to sense all pressure variations in the ram cylinders 6, 6' and, accordingly, emit an electric signal when such variations are sensed. The electric signals emitted by gauge 22 are fed into a bridge circuit 2 3 of a controller 21. Amplfier 24, associated with bridge 23, is adapted to emit an actuating signal for energizing solenoid valve 15. As further seen in the figure, the free end of rod 20, distal from cylinder 14, is attached to a potentiometer 25 which, in turn, is in circuit with bridge 23.

Having set forth the structural features of the invention, the sequence of opera-tion will now be described.

Operation Prior to the beginning of the rolling ope-ration proper, the desired clearance and parallelism between working rolls 4, 4 is set by means of energizing the screwdown motors 9, 9'. The pressure in the screwdown circuit and in the cylinders 13, 13' is adapted to maintain the work roll 4 in balance in its desired position with respect to work roll 4'. The pressure signal fed into bridge 23 from gauge 22 and the effect of the resistance of potentiometer 25, as set by the pre-operational position of rod 2 cancel each other and as a result, no actuating signal appears at the output of amplifier 24.

As the rolling mill is started and work is fed in between rolls 4, 4, the latter are exposed to a separating force causing an elastic deformation of the work rolls. The deformation, as it is well known, is proportional to the separating force and to the prevailing hydraulic pressure. Consequently, the hydraulic pressure will momentarily increase in the clampdown circuit in proportion to the force separating the work rolls 4, 4.

The increase of pressure in the clampdown circuit due to the separation of the work rolls has two immediate effects: (1) the electric signal fed from pressure gauge 22 into bridge '23 is increased; (2) the rod 20 is displaced in the direction of the arrow 19 due to the increase of pressure in the right hand chambers of actuating cylinders 13, 13'. The displacement of rod 20 causes potentiometer 25 to change its previous, balanced value. The comparison of the new signal from gauge 22 and the new value of potentiometer 25 results in a correcting output signal from bridge 23 through amplifier 24 energizing solenoid valve 15. Upon energization, the valve 15 establis'hes communication between the left hand chamber of cylinder 14 and pressure accumulator 16 causing hydraulic liquid to be injected into control cylinder 14. The new pressure in the left hand chamber of cylinder 14 is sufficiently large to overcome the pressure in the screw circuit and thus, in cylinders 13, 13'. As a consequence, rod 20 will now move towards its original position.

The return motion of rod 20 has two immediate effects: First, the volume of the right hand chambers gradually decreases causing the hydraulic liquid to be displaced therefrom. The increased pressure in the clampdown circuit results in an expansion of ram cylinders 6, 6' forcing roll 4 to assume its preset position. Secondly, the potentiometer is moved back by rod 20 towards its original setting.

As rod 20 reaches, during its return travel, the position it had prior to the rolling operation, ram cylinders 6, 6' will re-expand to their original value, and as a final result, the originally set constant for the roll passes will be re-established. As the original rolling constant is again obtained, the now larger pressure signal from gauge 22 and the voltage from returning potentiometer 25 will once again cancel out, cutting off the output signal to valve 15. Thus, valve 15 will close, maintaining the servo pressure in the left hand chamber of control cylinder 14 to balance the now elevated pressure in the clampdown circuit. I

During the rolling passes more or less significant irregularities in the thickness of the sheet cause a fluctuating deformation and separation of the rolls and hence a similarly fluctuating pressure in the clampdown circuit. The inventive compensating system described hereinabove is prominently effective in instantaneously counteracting such fluctuations to maintain the pass constant. Increases in the roller separating forces are counteracted in a way identical to that described hereinbefore. On the other hand, when the separating force is reduced, the rod 20 will move to the right and the output signal from amplifier 24 will energize valve 15 in such a manner that the threeway valve 15 establishes communication between the left hand chamber of control 14 and reservoir 18. Thus, fluid is drained from cylinder 14 causing a pressure drop therein. The screw-down pressure in the right hand chambers of cylinders 13, 13' will now be capable of overcoming the servo pressure in cylinder 14 causing rod 20 to return in a leftward movement. The signal transmitted from amplifier 24 to valve 15 will be cut off as soon as the decreased ressure in the screwdown circuit re-established the rolling clearance originally set.

In order to ensure an instantaneous and rapid return movement of rod 20 it is desirable that the volume/ time admission of fluid to or withdrawal from cylinder 14 be as large as practically possible. It is within the scope of the invention to replace cylinder 14 with a double acting cylinder wherein, with the appropriate use of a threeway valve and additional hydraulic conduit to the right chamber, a withdrawal of liquid from or the admission to one of the chambers is simultaneously accompanied by admission of liquid to, or withdrawal from the other chamber, respectively.

it is seen from the fore-going specification that the invention provides a rolling pressure compensating system that operates with the exclusion of the screwdown mechanism and having therefore a low inertia, is capable of instantaneous response and correction.

Although only a single embodiment of the invention has been depicted and described, it will be apparent that this embodiment is illustrative in nature and that a number of modifications in the apparatus and variations in its end use maybe effected without departing from the spirit or scope of the invention as defined in the appended claims.

What I claim is:

1. A system for compensating for the deformation of working rolls in rolling mills of the type including a screwdown mechanism associated with ram cylinders through a hydraulic screwdown circuit containing a constant volume of hydraulic fluid to adjust the roll supporting chocks to a roll clearance of predetermined value, comprising (a) expansible equalizing means communicating with said screwdown circuit and adapted to receive therefrom and release thereinto amounts of said fluid as the pressure in said circuit varies in response to the changes in said clearance caused by fluctuating roll separating forces,

(b) hydraulic servo means adapted to cause contraction or expansionvof said equalizing means,

(0) electric circuit means for sensing and comparing the variation of pressure in said ram cylinders and the variation of expansion or contraction of said equalizing means, said electric circuit means, responsive to the comparison of said variations adapted to energize said hydraulic servo means to return said equalizing means in a position where the pressure in said screwdown circuit counteracts said separating forces to such an extent as to re-establish said predetermined clearance.

2. A system as defined in claim 1, wherein said equalizing means includes (1) expansible equalizing chamber means communicating with said screwdown circuit and adapted to receive therefrom and release thereinto amounts of said fluid as the pressure in said circuit varies in response to changes of said clearance caused by fluctuating roll separating forces and (2) follower means mechanically connected to said expansible chamber means and adapted to be displaced by the change of volume of said expansible chamber means and cause a change of volume thereof when actuated by said hydraulic servo means, said follower means further adapted to generate, when being displaced, a changing signal in said circuit means.

3. A system as defined in claim 1, wherein said hydraulic servo system includes (1) expansible control chamber means operatively associated with said equalizing means to cause said last named means to expand or contract,

(2) solenoid valve means adapted to admit to or drain hydraulic fluid from said control chamber means to cause expansion or contraction thereof, said solenoid valve means being energized by said electric circuit means.

4. A system as defined in claim 1, including gauge means communicating with said screwdown circuit and adapted to generate electric signals proportional to the pressure change in said ram cylinders.

5. A system as defined in claim 1, wherein said equalizing means includes (1) at least one equalizing cylinder having a slideable piston therein,

(2) an expansible chamber defined by the inside wall of said cylinder and said piston, said chamber communicating with said screwdown circuit,

(3) a piston rod rigidly attached to said piston,

said hydraulic servo means includes l) a control cylinder axially aligned with said equalizing cylinder and having a slideable piston therein,

(2) an expansible chamber defined by the inside wall of said control cylinder and by the piston slideable therein,

( 3) solenoid valve means adapted to admit to or drain hydraulic liquid from said control cylinder, said piston rod being rigidly attached to said piston slideable in said control cylinder.

6. A system as defined in claim 2, wherein said equalizing chamber means includes at least one cylinder, each associated with a ram cylinder, said follower mean includes a piston slideably disposed in said cylinder and a piston rod rigidly attached thereto and operatively con nected to said hydraulic servo means, said rod adapted to be displaced by pressure changes in said cylinder and by the action of said hydraulic servo means.

7. A system as defined in claim 3, wherein said ex- References Cited by the Examiner UNITED STATES PATENTS 2,056,409 10/ 1936 Ross 72245 2,119,390 5/1938 Ivensen 72245 2,523,553 9/1950 Blain 72-245 2,998,238 8/1961 Kenline 72-20 3,075,417 1/1963 Blain 72240 CHARLES W. LANHAM, Primary Examiner.

G. P. CROSBY, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,286,495 November 22, 1966 Lucien Diolot It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 14, for "mean" read means column 6, l1ne 6, for "chaging" read changing Signed and sealed this 12th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. A SYSTEM FOR COMPENSATING FOR THE DEFORMATION OF WORKING ROLLS IN ROLLING MILLS OF THE TYPE INCLUDING A SCREWDOWN MECHANISM ASSOCIATED WITH RAM CYLINDERS THROUGH A HYDRAULIC SCREWDOWN CIRCUIT CONTAINING A CONSTANT VOLUME OF HYDRAULIC FLUID TO ADJUST THE ROLL SUPPORTING CHOCKS TO A ROLL CLEARANCE OF PREDETERMINED VALUE, COMPRISING (A) EXPANSIBLE EQUALIZING MEANS COMMUNICATING WITH SAID SCREWDOWN CIRCUIT AND ADAPTED TO RECEIVE THEREFROM AND RELEASE THEREINTO AMOUNTS OF SAID FLUID AS THE PRESSURE IN SAID CIRCUIT VARIES IN RESPONSE TO THE CHANGES IN SAID CLEARANCE CAUSED BY FLUCTUATING ROLL SEPARATING FORCES, (B) HYDRAULIC SERVO MEANS ADAPTED TO CAUSE CONTRACTION OR EXPANSION OF SAID EQUALIZING MEANS, (C) ELECTRIC CIRCUIT MEANS FOR SENSING AND COMPARING THE VARIATION OF PRESSURE IN SAID RAM CYLINDERS AND THE VARIATION OF EXPANSION OR CONTRACTION OF SAID EQUALIZING MEANS, SAID ELECTRIC CIRCUIT MEANS, RESPONSIVE TO THE COMPARISON OF SAID VARIATIONS ADAPTED TO ENERGIZE SAID HYDRAULIC SERVO MEANS TO RETURN SAID EQUALIZING MEANS IN A POSITION WHERE THE PRESSURE IN SAID SCREWDOWN CIRCUIT COUNTERACTS SAID SEPARATING FORCES TO SUCH AN EXTENT AS TO RE-ESTABLISH SAID PREDETERMINED CLEARANCE. 